ALL is due to malignant transformation of an abnormal progenitor cell, which then expands to form a clone of similar progeny by indefinite replication. This is called Clonal pathogenesis.
In ALL this occurs in committed lymphoid precursor cells.
Events leading to transformation are complex and multifactorial.
ALL results from spontaneous mutations in in lymphoid cells of T or B cell lineage or in their precursor cells
Causative mutations may occur years before the clinical presentation with leukemia.
